In object-oriented programming sending a message to an object (to invoke a method) is equivalent to calling a procedure in traditional programming languages, except that the actual code executed may only be selected at run time depending on the class of the object. Thus, in response to the message "drawSelf", the method code invoked would be different if the target object were a circle or a square.

Last updated: 1995-02-16

message board

bulletin board system

Message Digest 5


The message digest function defined in RFC 1321.

Last updated: 1996-08-04

message digest function

one-way hash function

Message Handling System

<messaging, standard>

(MHS) The standard defined by ITU-T as X.400 and by ISO as Message-Oriented Text Interchange Standard (MOTIS). MHS is the X.400 family of services and protocols that provides the functions for global electronic mail transfer among local mail systems and MTAs.

It is used by CompuServe, among others.

Last updated: 1996-09-25

message passing

One of the two techniques for communicating between parallel processes (the other being shared memory).

A common use of message passing is for communication in a parallel computer. A process running on one processor may send a message to a process running on the same processor or another. The actual transmission of the message is usually handled by the run-time support of the language in which the processes are written, or by the operating system.

Message passing scales better than shared memory, which is generally used in computers with relatively few processors. This is because the total communications bandwidth usually increases with the number of processors.

A message passing system provides primitives for sending and receiving messages. These primitives may by either synchronous or asynchronous or both. A synchronous send will not complete (will not allow the sender to proceed) until the receiving process has received the message. This allows the sender to know whether the message was received successfully or not (like when you speak to someone on the telephone). An asynchronous send simply queues the message for transmission without waiting for it to be received (like posting a letter). A synchronous receive primitive will wait until there is a message to read whereas an asynchronous receive will return immediately, either with a message or to say that no message has arrived.

Messages may be sent to a named process or to a named mailbox which may be readable by one or many processes.

Transmission involves determining the location of the recipient and then choosing a route to reach that location. The message may be transmitted in one go or may be split into packets which are transmitted independently (e.g. using wormhole routing) and reassembled at the receiver. The message passing system must ensure that sufficient memory is available to buffer the message at its destination and at intermediate nodes.

Messages may be typed or untyped at the programming language level. They may have a priority, allowing the receiver to read the highest priority messages first.

Some message passing computers are the MIT J-Machine, the Illinois Concert Project and transputer-based systems.

Object-oriented programming uses message passing between objects as a metaphor for procedure call.

Last updated: 1994-11-11

Message Passing Interface

<communications, protocol>

A de facto standard for communication among the nodes running a parallel program on a distributed memory system. MPI is a library of routines that can be called from Fortran and C programs. MPI's advantage over older message passing libraries is that it is both portable (because MPI has been implemented for almost every distributed memory architecture) and fast (because each implementation is optimised for the hardware it runs on).


Last updated: 1997-06-09

message switching

store and forward

Message Transfer Agent


(MTA, Mail Transfer Agent) Any program responsible for delivering e-mail messages. Upon receiving a message from a Mail User Agent or another MTA, often by SMTP over the Internet, it stores it temporarily locally and analyses the recipients and delivers it to any local addressees and/or forwards it to other remote MTAs (routing) for delivery to remote recipients. In either case it may edit and/or add to the message headers.

The most widely used MTA for Unix is sendmail, which communicates using SMTP.

[Other OSes?]

RFC 2821 (SMTP) expands MTA as "Mail Transfer Agent" though this is less common. Alternatives with "Transport" are also seen but less correct.

Last updated: 2007-06-01

Message Transport Agent

Message Transfer Agent

Messaging Application Programming Interface


(MAPI) A messaging architecture and a client interface component for applications such as electronic mail, scheduling, calendaring and document management. As a messaging architecture, MAPI provides a consistent interface for multiple application programs to interact with multiple messaging systems across a variety of hardware platforms.

MAPI provides better performance and control than Simple MAPI, Common Messaging Calls (CMC) or the Active Messaging Library. It has a comprehensive, open, dual-purpose interface, integrated with Microsoft Windows. MAPI can be used by all levels and types of client application and "service providers" - driver-like components that provide a MAPI interface to a specific messaging system. For example, a word processor can send documents and a workgroup application can share and store different types of data using MAPI.

MAPI separates the programming interfaces used by the client applications and the service providers. Every component works with a common, Microsoft Windows-based user interface. For example, a single messaging client application can be used to receive messages from fax, a bulletin board system, a host-based messaging system and a LAN-based system. Messages from all of these systems can be delivered to a single "universal Inbox".

MAPI is aimed at the powerful, new market of workgroup applications that communicate with such different messaging systems as fax, DEC All-In-1, voice mail and public communications services such as AT&T Easylink Services, CompuServe and MCI MAIL. Because workgroup applications demand more of their messaging systems, MAPI offers much more than basic messaging in the programming interface and supports more than local area network (LAN)-based messaging systems. Applications can, for example, format text for a single message with a variety of fonts and present to their users a customised view of messages that have been filtered, sorted or preprocessed.

MAPI is built into Windows 95 and Windows NT and can be used by 16-bit and 32-bit Windows applications. The programming interface and subsystem contained in the MAPI DLL provide objects which conform to the Component Object Model. MAPI includes standard messaging client applications that demonstrate different levels of messaging support.

MAPI provides cross platform support through such industry standards as SMTP, X.400 and Common Messaging Calls. MAPI is the messaging component of Windows Open Services Architecture (WOSA).

[Correct expansion? Relatonship with Microsoft?]

Last updated: 1997-12-03

Messaging Applications Programming Interface

Messaging Application Programming Interface


/mes-dos/ (Or MS-DOG, Messy-DOS, mess-dross, mess-loss, mush-dos) Derisory term for MS-DOS. Often followed by the ritual banishing "Just say No!"

Most hackers (even many MS-DOS hackers) loathe MS-DOS for its single-tasking nature, its limits on application size, its nasty primitive interface, and its ties to IBMness (see fear and loathing).

In Ireland and the UK it is sometimes called "Domestos" after a brand of toilet cleanser.

[Jargon File]

Last updated: 1994-11-16

Nearby terms:

meshMESI protocolmessagemessage boardMessage Digest 5message digest function

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